RNA silencing is a fundamental mechanism of gene regulation that uses double-stranded RNA (dsRNA) derived 21- to 28-nucleotide (nt) small RNAs to guide mRNA degradation, control mRNA translation or chromatin modification. Recently, several hundred novel genes were identified in plants and animals that encode transcripts that contain short dsRNA hairpins.
Defined 22-nt RNAs, referred to as microRNAs (miRNAs), are reported to be excised by dsRNA specific endonucleases from the hairpin precursors. The miRNAs are incorporated into ribonucleoprotein particles (miRNPs).
Plant miRNAs target mRNAs containing sequence segments with high complementarity for degradation or suppress translation of partially complementary mRNAs. Animal miRNAs appear to act predominantly as translational repressors. However, animal miRNAs have also been reported to guide RNA degradation. This indicates that animal miRNPs act like small interfering RNA (siRNA)-induced silencing complexes (RISCs).
Understanding the biological function of miRNAs requires knowledge of their mRNA targets. Bioinformatic approaches have been used to predict mRNA targets, among which transcription factors and proapoptotic genes were prominent candidates. Processes such as Notch signaling, cell proliferation, morphogenesis and axon guidance appear to be controlled by miRNA genes.
Therefore, there is a need for materials and methods that can help elucidate the function of known and future microRNAs. Due to the ability of microRNAs to induce RNA degradation or repress translation of mRNA which encode important proteins, there is also a need for novel compositions for inhibiting microRNA-induced cleavage or repression of mRNAs.